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DOE OSTI · 3000532

Atomically Revealing Bulk Point Defect Dynamics in Hydrogen‐Driven γ‐Fe 2 O 3 → Fe 3 O 4 → FeO Transformation

Wu, Yupeng [State Univ. of New York (SUNY), Binghamton, NY (United States)]·Wu, Dongxiang [State Univ. of New York (SUNY), Binghamton, NY (United States)]·Zhu, Wenhui [State Univ. of New York (SUNY), Binghamton, NY (United States)]·Chen, Xiaobo [State Univ. of New York (SUNY), Binghamton, NY (United States)]·Zhou, Zhikang [State Univ. of New York (SUNY), Binghamton, NY (United States)]·Liang, Zhilu [State Univ. of New York (SUNY), Binghamton, NY (United States)]·Ye, Shuonan [State Univ. of New York (SUNY), Binghamton, NY (United States)]·Li, Meng R. [Brookhaven National Laboratory (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)] (ORCID:0000000227454016)·Tong, Xiao [Brookhaven National Laboratory (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)]·Kisslinger, Kim [Brookhaven National Laboratory (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)]·Hwang, Sooyeon [Brookhaven National Laboratory (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)]·Zakharov, Dmitri [Brookhaven National Laboratory (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)]·Sharma, Renu [National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)]·Yang, Judith C. [Brookhaven National Laboratory (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)]·Zhou, Guangwen [State Univ. of New York (SUNY), Binghamton, NY (United States)] (ORCID:000000029243293X)
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Abstract

Understanding how point defects in the bulk govern redox transformations is essential for advancing hydrogen-based metal production and designing high-performance oxide materials. This study reveals the atomic-scale mechanisms driving hydrogen-induced reduction of γ-Fe 2 O 3 to Fe 3 O 4 , focusing on how bulk vacancy dynamics dictate structural evolution and reaction kinetics. A key finding is the pronounced contrast in defect behavior between the two oxides: in γ-Fe 2 O 3 , intrinsic Fe vacancies promote oxygen vacancy clustering, destabilizing the local lattice and driving nanopore formation. In contrast, Fe 3 O 4 exhibits a higher oxygen vacancy formation energy and lacks intrinsic Fe vacancies, suppressing vacancy aggregation and maintaining a dense, pore-free structure. This divergence governs distinct reduction pathways—γ-Fe 2 O 3 undergoes an interface-reaction-limited transformation confined to the γ-Fe 2 O 3 /Fe 3 O 4 boundary, while Fe 3 O 4 supports a uniform increase in oxygen vacancy concentration, enabling bulk-phase reduction to lower-oxide FeO. Integrated in situ electron microscopy and density functional theory modeling uncover a vacancy-mediated mechanism, where synergistic cation-anion vacancy dynamics steer microstructure evolution and phase progression. These insights highlight the critical role of vacancy dynamics in controlling oxide reactivity and offer a pathway toward vacancy engineering to enhance reduction kinetics in hydrogen metallurgy and to tailor porosity, reactivity, and structural resilience in oxide-based catalysts and energy materials.

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36 MATERIALS SCIENCEhydrogen direction reduction of iron orein situ environmental transmission electron microscopyphase transformationsvacancy

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Wu, Yupeng [State Univ. of New York (SUNY), Binghamton, NY (United States)], Wu, Dongxiang [State Univ. of New York (SUNY), Binghamton, NY (United States)], Zhu, Wenhui [State Univ. of New York (SUNY), Binghamton, NY (United States)], Chen, Xiaobo [State Univ. of New York (SUNY), Binghamton, NY (United States)], Zhou, Zhikang [State Univ. of New York (SUNY), Binghamton, NY (United States)], Liang, Zhilu [State Univ. of New York (SUNY), Binghamton, NY (United States)], Ye, Shuonan [State Univ. of New York (SUNY), Binghamton, NY (United States)], Li, Meng R. [Brookhaven National Laboratory (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)] (ORCID:0000000227454016), Tong, Xiao [Brookhaven National Laboratory (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)], Kisslinger, Kim [Brookhaven National Laboratory (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)], Hwang, Sooyeon [Brookhaven National Laboratory (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)], Zakharov, Dmitri [Brookhaven National Laboratory (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)], Sharma, Renu [National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)], Yang, Judith C. [Brookhaven National Laboratory (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)], Zhou, Guangwen [State Univ. of New York (SUNY), Binghamton, NY (United States)] (ORCID:000000029243293X). 2025-10-21. Atomically Revealing Bulk Point Defect Dynamics in Hydrogen‐Driven γ‐Fe 2 O 3 → Fe 3 O 4 → FeO Transformation. https://doi.org/10.1002/adfm.202519406

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